bjoernager/rust
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Remove more needless leb128 coding for enum variants

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This removes emit_enum_variant and the emit_usize calls that resulted
in. In libcore this eliminates 17% of leb128, taking us from 8964488 to
7383842 leb128's serialized.
This commit is contained in:
Mark Rousskov 2024-01-09 19:51:18 -05:00
parent 5e8f67bbc9
commit 1d2005be71
3 changed files with 36 additions and 35 deletions
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33
compiler/rustc_serialize/src/serialize.rs
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@ -70,14 +70,6 @@ pub trait Encoder {
}
fn emit_raw_bytes(&mut self, s: &[u8]);
fn emit_enum_variant<F>(&mut self, v_id: usize, f: F)
where
F: FnOnce(&mut Self),
{
self.emit_usize(v_id);
f(self);
}
}
// Note: all the methods in this trait are infallible, which may be surprising.
@ -132,10 +124,6 @@ pub trait Decoder {
fn read_raw_bytes(&mut self, len: usize) -> &[u8];
// Although there is an `emit_enum_variant` method in `Encoder`, the code
// patterns in decoding are different enough to encoding that there is no
// need for a corresponding `read_enum_variant` method here.
fn peek_byte(&self) -> u8;
fn position(&self) -> usize;
}
@ -372,15 +360,18 @@ impl<'a, D: Decoder> Decodable<D> for Cow<'a, str> {
impl<S: Encoder, T: Encodable<S>> Encodable<S> for Option<T> {
fn encode(&self, s: &mut S) {
match *self {
None => s.emit_enum_variant(0, |_| {}),
Some(ref v) => s.emit_enum_variant(1, |s| v.encode(s)),
None => s.emit_u8(0),
Some(ref v) => {
s.emit_u8(1);
v.encode(s);
}
}
}
}
impl<D: Decoder, T: Decodable<D>> Decodable<D> for Option<T> {
fn decode(d: &mut D) -> Option<T> {
match d.read_usize() {
match d.read_u8() {
0 => None,
1 => Some(Decodable::decode(d)),
_ => panic!("Encountered invalid discriminant while decoding `Option`."),
@ -391,15 +382,21 @@ impl<D: Decoder, T: Decodable<D>> Decodable<D> for Option<T> {
impl<S: Encoder, T1: Encodable<S>, T2: Encodable<S>> Encodable<S> for Result<T1, T2> {
fn encode(&self, s: &mut S) {
match *self {
Ok(ref v) => s.emit_enum_variant(0, |s| v.encode(s)),
Err(ref v) => s.emit_enum_variant(1, |s| v.encode(s)),
Ok(ref v) => {
s.emit_u8(0);
v.encode(s);
}
Err(ref v) => {
s.emit_u8(1);
v.encode(s);
}
}
}
}
impl<D: Decoder, T1: Decodable<D>, T2: Decodable<D>> Decodable<D> for Result<T1, T2> {
fn decode(d: &mut D) -> Result<T1, T2> {
match d.read_usize() {
match d.read_u8() {
0 => Ok(T1::decode(d)),
1 => Err(T2::decode(d)),
_ => panic!("Encountered invalid discriminant while decoding `Result`."),